Fully agree on templates but I use Phlex to build UIs with pure Ruby on the server side. A pleasure to work with. And with something like Datastar, reactive UIs with practically no js.
I really don't like Hotwire and FE history (I'm playing with htmx, Datastar, Phlex and love it) but the ActiveSupport autoloader -> to Zeitwerk migration was pretty much something in the background, an implementation detail, at least in my experience. Most devs don't even know what is all this about.